The present invention concerns a chassis measuring apparatus for vehicles such as for motor vehicles, and a method of chassis measurement for vehicles.
For reasons of travel safety of a vehicle and in order to avoid excessive wear at the wheels of the vehicle, checking the correct alignment of each wheel is an important procedure. That is effected by a process involving axle measurement. Axle measurement is effected both in the manufacturing plant where a vehicle is produced and also in workshops which are specifically equipped for that purpose.
In practice, inter alia optical methods have been employed for chassis axle measurement, which involves detecting accurate alignment or non-alignment of the wheel by means of a camera and by means of reflectors which are fitted to the wheels. If misalignment of the wheel or wheels is detected, then the vehicle is lifted by means of a lift platform on to which the vehicle is driven before the measuring operation is carried out. Adjustment is then effected, the vehicle is lowered and the settings made are checked. If it is found that the adjustment has not been correctly carried out, the vehicle has to be lifted once again for a further adjustment operation. That procedure therefore takes up a great deal of time and is accordingly cost-intensive.
In addition, the chassis-checking procedure or chassis adjustment in the vehicle manufacturing plant involves the problem that the individual checking and setting operations have to be carried out in rapid succession, corresponding to the large number of items being produced. In the case of the chassis measuring apparatuses which are involved in a practical context however, the vehicle can be driven on to the vehicle lift platform only from one end thereof, because the axle measuring device is stationarily arranged at the other end. That means that the next vehicle to be checked has to wait until the vehicle which is just being measured has actually left the vehicle lift platform. That means that the chassis measuring procedure takes up a disproportionately great amount of time, which increases manufacturing costs.
An object of the present invention is to provide an apparatus for vehicle chassis measurement, which permits rapid adjustment of the chassis of the vehicle while at the same time checking the adjustment procedure.
Another object of the present invention is to provide a method of measuring a vehicle chassis, which entails a rapid operating procedure that is easy to implement, combined with the possibility of accurate results.
The foregoing and other objects is attained by the invention set forth herein.
Designing the axle measurement lifting device with two lifting stages which are actuable reversibly independently of each other affords the possibility of using the one lifting stage, the first lifting stage, to adjust the axle measuring unit of the axle measurement device at the vertical height which is required for the measuring procedure. If in particular the axle measuring unit involves an optical measuring device, then vertical adjustment of the axle measuring unit is effected in accordance with the position of the associated reflectors at the wheels. If, after a defect in alignment of the individual wheels has been detected, a setting operation is required, then the vehicle can be lifted with the vehicle lift platform. In that situation, at the same time and by way of the second lifting stage of the axle measurement lifting device, the axle measuring unit which is set in respect of its vertical height in relation to the reflectors at the wheels of the vehicle is also lifted without in that situation the vertical adjustment thereof being altered. That means that time-consuming re-adjustment of the axle measuring unit is not required. Furthermore, there is the possibility of simultaneously effecting the setting operation while the measurement procedure is continuing so that the setting operation can be directly monitored and possibly altered once again.
In principle, there is the possibility of firstly raising the vehicle lift platform, detecting the vertical position thereof, and then vertically displacing the second lifting stage of the axle measurement lifting device in a controlled manner to the level of the vehicle lift platform. That involves a certain time delay as firstly the vehicle lift platform is raised, the position thereof is detected and then the second lifting stage of the axle measurement lifting device is raised. In order to be able to implement the setting operation in such a fashion as to save time, it is advantageous and a preferred feature of the invention if the lifting drive of the vehicle lift platform and the lifting drive of the second lifting stage of the axle measurement lifting device are actuable in such a way that they are displaceable synchronously. That provides that the vehicle lifting platform and the second lifting stage of the axle measurement lifting device are raised at the same time so that the setting operation can be effected immediately after the desired height of the vehicle lift platform has been reached.
In order to be able to flexibly displace the first lifting stage on the one hand and the second lifting stage and the vehicle lift platform on the other hand, a further preferred feature of the invention provides that the drive of the first lifting stage of the axle measurement lifting device is reversibly actuable independently of the drive of the second lifting stage and the vehicle lift platform.
Depending on the respective factors involved, quite different drives can be adopted for the vehicle lift platform and the lifting stages of the axle measurement lifting device. In accordance with another preferred feature of the invention a particularly inexpensive option for a drive provides that the vehicle lift platform and at least the second lifting stage of the axle measurement lifting device each have at least one respective piston-cylinder unit as the drive. The piston-cylinder units can be operated pneumatically or hydraulically.
In order to be able to implement the above-mentioned synchronous raising operation between the second lifting stage of the axle measurement lifting device and the vehicle lift platform, it is advantageous if the piston-cylinder unit of the vehicle lift platform is connected in series with the piston-cylinder unit of the second lifting stage of the axle measurement lifting device, for synchronous raising movement to the same heightwise level.
The drive of the second lifting stage of the axle measurement lifting device can also be formed by at least one piston-cylinder unit.
Different design configurations which are also adapted to the factors involved can be adopted for the construction of the vehicle lift platform and the first and/or second lifting stage. It has been found to be particularly advantageous if the vehicle lift platform and/or the first lifting stage and/or the second lifting stage of the axle measurement lifting device are in the form of a scissor platform.
In general, the axle measuring device is arranged stationarily in front of the nose or the tail of the vehicle. The consequence of this arrangement, when the axle measuring device stands upright, is that the vehicle cannot move on to the vehicle lift platform and off again in one direction of movement, as the axle measuring device is in the way. That is a disadvantage in particular if the chassis measuring apparatus is used in a vehicle manufacturing plant in which the vehicles have to be checked in rapid succession. In order in this case also to be able to measure and possibly re-adjust as many chassis of vehicles as possible, with the apparatus according to the invention, in the shortest possible time, it is advantageous if the vehicle lift platform and the axle measurement lifting device are arranged on a common foundation provided with at least one recess for the axle measurement lifting device, into which it can be lowered, in its inoperative condition, to such an extent that it is aligned at least with the upper level of the trackway surface of the vehicle lift platform in the lowered condition. That affords the possibility that the vehicle on the vehicle lift platform can drive off the vehicle lift platform over the axle measuring device.
In order in that case to avoid damage to the axle measuring device, it can further be provided that the top of the axle measuring device is provided with a plate which at least approximately closes off the recess in the foundation.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment.